Human Nature: Science, Technology, and Life.

Body Parts From Trash

We cover a lot of fancy technology in this blog. But sometimes the most ingenious and far-reaching gadgetry is the least fancy.

A few recent cases: First we looked at incubators made from car parts. Then we learned about ugly standardized glasses you can adjust to your eyesight with a pump. In both cases, engineers are improving life in the developing world by using cheap, available materials instead of cutting-edge technology. But why stop with external devices? Why not extend the low-tech, high-utility revolution into the human body?

That's what Thailand's Prostheses Foundation is doing for thousands of Thais who have lost their legs to land mines, diabetes, and birth defects. "In 17 years, the foundation says it has given away more than 30,000 legs," Agence France Presse reports. In the United States, prosthetic legs cost $10,000 to $50,000 or more. So how can the Prostheses Foundation afford to give them away?

Answer:

It is the recycled materials that make the project workable, Thamrongrat [the foundation's vice chairman] said, as they they keep costs down and allow the foundation to make and distribute more legs. The foundation asks people to donate materials that can be used in the limbs, such as beer cans and aluminum pots. A prosthetic for below the knee costs the foundation 1,000 baht (about 28 dollars) to make, Thamrongrat said. It would cost the government 10,000 baht to build a similar one.

Example:

Twelve-year-old Matoha Dosare was born with no right leg, but thanks to recycled soft drink cans and some old stockings, he now has a new limb and new-found independence. ... Matoha has had three new legs fitted in the last two years, with the metal in the joints coming from the donated bottle caps and tins. The nylon from the stockings is used in the sculpting process to help form the legs.

Three prosthetic legs in two years? That sounds bad. The downside of getting a leg made from soda cans is that aluminum doesn't last as long as steel. But if the upside is a 90 percent cut in production cost, the kid comes out ahead, because he can get those three legs for one-third the cost of a government-issued prosthesis. And since he's growing, each new leg can be adjusted to his increasing size.

But here's the really interesting twist:

One prosthetic offered is the "farmer's leg," which uses more steel and ends in a stump with tire treads on the bottom rather than a false foot. This was created because farmers complained the foot got stuck in the mud. ...

The prosthetic extension designed to mimic a human foot did what feet sometimes do: It got stuck. So the leg makers replaced it with an extension designed for performance in mud. They made a foot more like a tire. In fact, they made a foot from a tire. It lacks the mobility of a healthy human foot. But for farming in Thailand, it has a better shape.

Ankles Away

Looks like I missed a joint.

A couple of months ago, I wrote about the artificial parts we've been putting into people: hips, knees, shoulders, spinal discs, and elbows. U.S. government stats show more than 1 million such replacements per year. Piece by piece, we're mechanizing the body.

Next up: ankles.

Lauran Neergard of the AP has the story. There's a healthy (actually, an unhealthy) market for new ankles: More than 200,000 patients go to doctors for ankle pain every year. The prevailing surgical option is to fuse the ankle bones, which gets rid of the friction, and therefore the pain, but skews the way you move your foot. That, in turn, increases the strain on other foot joints, causing more pain and more fusions.

So why hasn't ankle replacement become as popular as hip or knee replacement? Because ankles are smaller and have to shoulder (so to speak) more stress. The original generation of artificial ankles broke down under normal wear and tear. A new generation is just now taking off. They cost up to $50,000 but are designed to operate more like a natural ankle, which would avoid the downstream damage associated with fusion. Neergard explains how they work:

Each model is slightly different but consists of two attached parts. Surgeons drill a tunnel into the lower leg bone and slide in the stem of the artificial joint. A bottom piece connects to the top of the foot. Thin plastic hooked to one side functions as cartilage. Bone then grows into the implant, holding it in place. In Europe, doctors also can use a similar but three-piece artificial ankle, where the plastic cushion is free-floating.

So the artificial cushion relieves day-to-day strains on the ankle, while the body, through bone growth, adopts the new mechanism as its own. Biology absorbs technology. Very cool. Let's hope it works.

The Bio-artificial Industry

How do you feel about mass-producing and selling human tissue in machine form? I hope you like the idea. Because it's on the way.

A few days ago, the University of Michigan trumpeted a study validating the efficacy of its "bioartificial kidneys." In a clinical trial involving people with acute renal injury and failure, the kidney boosters cut the usual death rate (compared to patients using conventional "continuous renal replacement therapy") from two in three patients to one in three.

Pretty amazing. But just what is a "bioartificial" kidney? Here's U-M's description:

The bioartificial kidney includes a cartridge that filters the blood as in traditional kidney dialysis. That cartridge is connected to a renal tubule assist device [RAD], which is made of hollow fibers lined with a type of kidney cell called renal proximal tubule cells. These cells are intended to reclaim vital electrolytes, salt, glucose and water, as well as control production of immune system molecules called cytokines, which the body needs to fight infection. Conventional kidney dialysis machines remove these important components of blood plasma, along with toxic waste products, and cannot provide the immune regulation function of living cells. Initial testing in animals ... found the cells in the RAD perform the metabolic and hormonal functions lost in acute renal failure.

This is the point I've made in recent posts about biological pacemakers and limb regeneration. Prosthetics are nice, but flesh is better. That's why the U.S. Army is now funding tissue regeneration. Instead of trying to reengineer everything in biology, we're learning to borrow, cultivate, and replicate it. Let Mother Nature do the work: She already knows how to filter toxins while keeping what your body needs and regulating your systems.

David Humes, the professor behind the U-M study, is also the scientific founder of the company that's preparing to commercialize the RAD. He envisions the new paradigm this way:

[T]he nature of our new approach -- using living cells as therapeutic agents -- argues for the feasibility of developing whole classes of new cell-based and tissue engineered therapies. The ability to harness vital processes of cells, to target their living molecular machinery on restoring critical substances which have become disordered by disease, has vast implications for the future of medicine. The apparently successful use of living cells in this way validates our approach and should encourage others to investigate cell therapies for a range of disorders.

Technologically, this is a sensible and powerful idea. It will save lives. But as an inflection point in our thinking about human flesh, it's, well, pretty RAD. What we're getting into is not just the commercialization but the mass-production of body parts. It's a bit like PETA's campaign to commercialize lab-grown meat -- except that in this case, the meat will be human.

Where do we get the cells in the cartridge from? According to the American Society of Nephrology, they're "grown from donor kidneys." So we're starting with somebody's donated organ. Instead of transplanting it to one person, we're growing cells from it, which can then be farmed out to multiple patients. We're not just distributing the cells; we're incorporating them into what U-M calls a "living cell cartridge." It's bio -- it's artificial -- it's bio-artificial.

Like lab-grown meat, the living tissue in the cartridge may run into spoilage problems. U-M notes that its researchers are still working on the "challenges of mass producing, storing and shipping a living-cell device." But the goal, according to the nephrology society, is definitely "mass production." And the next step will be to repackage it as a "wearable kidney that performs natural functions unachievable through man-made technology alone." Real flesh, grown from somebody else, mass-produced, packaged into a cartridge, and worn on your body. Good luck sorting the bio from the artificial.

The Future of Flesh

One thing I hope to do in this blog is to keep connecting news stories and trends to each other. It's not enough to mock the idea of a civil right to body piercings. The larger theme of today's earlier post was the difference between necessary and elective body parts, and the difference between flesh and metal.

Both of those differences touch on an article in the current issue of Scientific American. Right now, the best we can do for amputees is fit them with prostheses designed to approximate normal limb motion. Such limbs don't feel anything, which in turn makes it harder to learn how to use them. The ideal solution isn't to outfit these people like cyborgs; it's to give them good old flesh. That's what the authors-Ken Muneoka, Manjong Han, and David Gardiner-are working on. They conclude that "we may be only a decade or two away from a day when we can regenerate human body parts."

The path will require many steps. At the moment, the authors are still working on inducing basic regeneration in mice. Growing larger structures-paws, and later arms-will be progressively more difficult. But in principle, the project should be doable, since it's modeled on an animal that already regenerates its own limbs: the salamander.

If we're going to start handing out new bodily civil rights, as the nipple-ring lawyer proposes, I'd put replacement flesh way ahead of ornamental metal.